In recent years technology has been developed for reflective type display devices, which efficiently utilize ambient light to enable the display of images even without a backlight; such displays are thin, lightweight, and have low power consumption. Such reflective type displays comprise a color filter in which reflective layers and color layers are formed in sequence on a substrate.
Also, semi-transmissive display devices, in which the reflective layer is formed as a semi-transmissive layer having optical transmissive properties, have also been developed. Such semi-transmissive display devices can be used as reflective type devices in bright environments, utilizing ambient light, and can be used as transmissive type display devices in dark environments, using a backlight.
As a method to form the reflective layer, conventionally, sputtering or vacuum evaporation methods have been used to deposit an aluminum alloy or silver alloy.
In Japanese Patent Publication No. H7-191211, a high-reflectivity conductive film and a transparent conductive film are stacked on a substrate, using the conductive film and photoconductive film, a coloring pattern is formed by means of an electro-photographic method, and the conductive film is used as a reflective layer.
Also, in Japanese Patent Publication No. H10-96811, at least three coloring layers each having different colors are formed on a substrate, enclosing a reflective layer between the substrate and the coloring layers. The upper portion of the coloring layers is evaporated by means of laser irradiation, and the lower portion of the coloring layers is exposed, to form a reflective type color filter.
In conventional methods which employ sputtering or vacuum evaporation techniques to form reflective layers, at least four photolithography processes are required to reach the stages of substrate surface treatment and coloring layer formation, thus incurring a large number of processes and considerable time, and causing decreases in production yields.
In the method in the above-noted Japanese Patent Publication No. H7-191211, the number of processes for coloring layer formation is less than for photolithography, but a photomask is required for formation of each coloring layer and of the black matrix, and vacuum evaporation equipment, corona charge equipment and other equipment are separately required. Also, because only electrically insulating material can be used as toner, further constraints are imposed.
In the method in the above-noted Japanese Patent Publication No. H10-96811, a photomask is not required, but the upper coloring layer may be affected by the lower coloring layer. And, because laser light is used for evaporation, fine patterning is difficult. Also, surface unevenness of approximately 3 μm occurs on the substrate processed surface, so that brightness irregularities due to the difference in thickness of the liquid crystal layer readily occur.
An object of this invention is to provide a method enabling the manufacture of a reflective type color filter and display device in a short time, using little energy and at low cost, without requiring photolithography or other complicated processes.